The mechanisms involved in the regulation of cyclic nucleotide concentrations, and the subsequent biological functions of the altered cyclic nucleotide levels will be studied in spermatozoa. These studies primarily will concentrate at a biochemical level, but they also will present a strong comparative aspect, with emphasis on general similarities in the regulation of sperm cyclic nucleotide metabolism in both vertebrate and invertebrate systems. A purified glycoprotein associated with the eggs of the sea urchin which causes dramatic elevations in sperm cyclic AMP concentrations will be characterized extensively at the biochemical level. Radiolabeled factor and antibody to the factor will be produced and used in various biological studies. The purified factor as well as cyclic nucleotides and other agents will be tested for effects on sea urchin sperm motility, respiration rates and the acrosome reaction. It will be determined whether or not the factor activates the cyclic AMP-dependent protein kinase as well as other enzymes, such as phosphodiesterase and guanylate cyclase. The effects of the factor on intracellular protein phosphorylation and the identification of sperm proteins phosphorylated will represent a major aspect of this project. The "activated" form of adenylate cyclase also will be compared biochemically to the enzyme with basal activity. Comparative work will involve studies on the effects of cyclic nucleotides, phosphodiesterase inhibitors and of other agents on hamster and guinea pig sperm motility and the acrosome reaction. Female (and egg) factors will be tested to determine whether or not they affect cyclic nucleotide metabolism in mammals, as well as in the sperm from other groups of animals, such as amphibians and fishes. The potential involvement of cyclic nucleotides in the initiation of sperm motility in the hamster, trout and horseshoe crab also will be studied. These studies should greatly aid in our understanding of the role of cyclic nucleotides in the regulation of sperm function.